1. Field of the Invention
The present invention relates to a technology for controlling a sheet post-processing device that automatically binds a plurality of printed sheets.
2. Description of the Related Art
Office automation (OA) equipment, such as a copier, has been proposed, which includes or is connected to a sheet post-processing device, such as a finisher. The sheet post-processing device performs an automated sheet post-processing on printed sheets, leading to effective office work. For example, a sheet post-processing device disclosed in Japanese Patent Application Laid-open No. H06-286931 is configured to bind sheets by stapling and gluing. Japanese Patent Application Laid-open No. 2005-239429 discloses a sheet post-processing device, i.e., a ring binding device, configured to punch sheets and bind the sheets with a ring member. Unlike the stapling and the gluing, the ring binding device described above is advantageous because the sheets bound with the ring member can be taken from the ring by simply opening the ring.
Because the volume (number) of printed sheets to be bound varies, it is desirable that printed sheets be bound with a ring member having an appropriate size corresponding to a total thickness of the sheets. For example, if 10 sheets are bound with a 100-sheet ring member, with which 100 sheets can be bound at maximum, the ring member is too large for the sheets and unnecessarily requires a space. On the other hand, if 50 sheets are bound with a 50-sheet ring member, with which 50 sheets can be bound at maximum, each sheet can hardly be turned over with ease. The maximum volume of sheets to be bound with a ring depends on the size of the ring (i.e., the diameter of the rings). If a thickness of each sheet is uniform, the total thickness of sheets is proportional to the volume of sheets. Therefore, on the condition that every sheet to be bound has the same thickness, the maximum volume of sheets to be bound corresponds to a maximum total thickness of the sheets.
However, according to Japanese Patent Application Laid-open No. 2005-239429, because the ring binding device employs a ring member of one size, sheets cannot be bound with the ring member having a size suitable for the total thickness of sheets.